Ignorance is not bliss when it comes to one big number for millennials: their net worth. The vast majority of millennials (73 percent of those 18 to 34) have no idea what they have versus what they owe, according to a new survey from Harris Poll conducted for online money manager Personal Capital (personalcapital.com).

John Piazza admits he is one of them, although the Chicago-based banking executive says he has a "decent idea" of his net worth (assets such as cash and mutual funds minus liabilities like student and credit card debt). Piazza estimates that about 80 percent of his friends do not have a handle on their total financial picture.

"It's time-consuming to gather all the disparate information together initially, and then it's a laborious process to update it going forward," Piazza says.

While it may be a hassle, not knowing where you stand now makes it much harder to plan for where you need to be later in life, especially for retirement, says Kyle Ryan, a certified financial planner, who is the head of advisory services at Personal Capital.

It is even harder to get a handle on the numbers for those who have an outsized vision of what they might inherit down the road - which might dim their motivation to save now. The Personal Capital survey on retirement readiness found that millennials expect to inherit about a million dollars, on average.

The average inheritance in the United States is just $177,000 according to a 2013 HSBC survey.

Counting on any kind of windfall, regardless of size, is a risky business. It certainly does not merit giving up on saving for retirement - as some 40 percent of millennials respondents did on Personal Capital's survey by saying they had no retirement plan of any kind started yet.

Some wealthy families are not even planning on handing down their fortunes. Big names from Warren Buffet to Bill Gates, to Kiss rockstar Gene Simmons have all publicly talked about giving the vast majority of their wealth to charity - not to their kids.

"I've worked with many high-net worth individuals, who behind closed doors admit openly that they have no intentions of actually leaving a large sum of money to their children, nor to anyone," says Shannah Compton Game, a Los Angeles-based certified financial planner who focuses on millennials. "This can be a rude awakening for a millennial who has planned on those funds to continue a lifestyle that they have been living."

Here are three tips on getting your finances on track now instead of waiting for your retirement fund to be handed to you on a silver platter:

1. Do the math

The average millennial needs to save upwards of $2 million to live a somewhat comfortable life in retirement, according to Compton Game.

Websites can help you figure out the average needs, including Personal Capital, Bankrate.com (bankrate.com) and AARP (bit.ly/20E5Sxk). Or you can talk to a fee-only financial planner and get specific advice.

2. Have a sit down with your parents

Do not assume you know how much money they have, or that it is going to you.

"It can be a hard conversation to start, but it's easier than having an expectation that isn't fulfilled," says Game.

You also have to consider the timeframe involved and factor in the uncertainty. Typical millennials in their 20s today would have parents who are a long way from retirement and, perhaps, 50 years from dying.

3. Save more

Even if your parents do intend to leave you an inheritance, saving money should still be your top priority. Build a solid emergency fund that can cover three-to-six months of expenses in a high-yield checking account. And contribute to some kind of retirement plan; even if your employer does not offer a 401(k) there are options for IRAs.

If you started contributing $100 a month at age 25 to a traditional IRA, and got a very modest 4 percent return, you would have more than $118,592 before taxes if you retired at age 65 based on Bankrate.com's retirement calculator.

(The author is a Reuters contributor. The opinions expressed are her own.)